Polishing pad having edge surface treatment

ABSTRACT

The present invention is directed to a polishing pad having a sublayer and a polishing layer. The surface of the outer peripheral edge of the sublayer can be at least partially treated to reduce the absorption or permeation of polishing fluid into the sublayer through the outer peripheral edge. The application of the surface treatment at least reduces the amount of polishing fluid absorbed by the sublayer of the polishing pad during the polishing process. The polishing pad of the present invention is useful in polishing microelectronic substrates and especially useful in chemical mechanical planarization of semiconductor wafers.

This application is a conversion of United States Provisional PatentApplication having Ser. No. 60/493,292, filed on Aug. 7, 2003.

The present invention is directed to a polishing pad having a sublayerand a polishing layer. The surface of the outer peripheral edge of thesublayer can be at least partially treated to reduce the absorption orpermeation of polishing fluid into the sublayer through the outerperipheral edge. The application of the surface treatment at leastreduces the amount of polishing fluid absorbed by the sublayer of thepolishing pad during the polishing process. The polishing pad of thepresent invention is useful in polishing microelectronic substrates andespecially useful in chemical mechanical planarization of semiconductorwafers.

It is typical to use polishing fluid, such as polishing slurry, inconjunction with a polishing pad to polish a microelectronic substrate.The polishing pad can comprise a stacked pad construction including asublayer. During the polishing process, it is advantageous to at leastreduce or minimize the adsorption of slurry into the sublayer.Absorption of slurry into the sublayer can alter or change thecompressibility of the sublayer. For example, if the sublayer is madeless compressible, the work surface of the pad construction may notadequately conform to the microelectronic substrate being polished,which can result in polishing performance which is not uniform acrossthe substrate. Furthermore, if the sublayer compressibility decreasesduring the process of polishing a series of wafers, the wafer-to-waferpolish consistency can be compromised.

There is a need in the art to develop a polishing pad that at leastreduces the absorption of polishing fluid into the sublayer of the pad.It is still further contemplated that it would be desireable to developsuch a polishing pad and means without significantly impacting thecompressibility of the sublayer.

It is noted that, as used in this specification, the singular forms “a,”“an,” and “the” include plural referents unless expressly andunequivocally limited to one referent.

For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

The present invention is directed to a polishing pad for use inpolishing a microelectronic substrate. Various pad constructionssuitable for use in the present invention are known in the art. Thepolishing pad can include a polishing layer and a sublayer. Thepolishing layer can be at least partially connected to the sublayer. Thesublayer can have an outer peripheral edge. At least a portion of theouter peripheral edge can be surface treated with a material thatreduces the ability of the outer peripheral edge of the sublayer toabsorb polishing fluid, such that permeation of polishing liquid intothe sublayer is reduced. In a non-limiting embodiment, the material canbe selected such that at least a portion of the surface of the outerperipheral edge of the sublayer is made substantially hydrophobic. In afurther non-limiting embodiment, the material can be selected such thatthe wettability of at least a portion of the surface of the outerperipheral edge of the sublayer is at least reduced.

A polishing pad can generally comprise a stacked layer constructionincluding at least a polishing layer and a sublayer. The polishing layercan function as the working surface of the pad such that the polishinglayer can at least partially interact with the microelectronic substrateto be polished and the polishing fluid. In alternate non-limitingembodiments, the material of the polishing layer can be selected suchthat the polishing layer is substantially impermeable to polishing fluidor substantially permeable to polishing fluid. In further non-limitingembodiments, the material of the polishing layer can be selected suchthat the polishing layer is substantially non-porous or substantiallyporous.

The polishing layer of the pad can be at least partially connected to asublayer. In a non-limiting embodiment, the sublayer of the pad canfunction as the bottom layer of the pad which can be attached to theplaten of a polishing apparatus. The material of the sublayer can beselected such that the sublayer is substantially permeable to polishingfluid. Further, the material of the sublayer can be selected such thatthe sublayer is substantially porous.

Non-limiting examples of suitable materials for the polishing layer caninclude but are not limited to particulate polymer and crosslinkedpolymer binder such as described in International Publication No. WO02/22309; particulate polymer and an organic polymer binder; sinteredparticles of thermoplastic resin as described in U.S. Pat. Nos.6,062,968; 6,117,000; and 6,126,532 describe; and pressure sinteredpowder compacts of thermoplastic polymer as described in U.S. Pat. Nos.6,231,434 B1, 6,325,703 B2, 6,106,754 and 6,017,265. Additionalnon-limiting examples of suitable materials for the polishing layer caninclude polymeric matrices impregnated with a plurality of polymericmicroelements, wherein each polymeric microelement can have a void spacewithin, as described in U.S. Pat. Nos. 5,900,164 and 5,578,362. Therelevant portions of the above-mentioned patents are incorporated hereinby reference.

In a non-limiting embodiment, the thickness of the polishing layer canvary widely depending on its composition. In alternate non-limitingembodiments, the polishing layer can have a thickness of at least 0.020inches, or at least 0.040 inches; or 0.150 inches or less, or 0.080inches or less.

In another non-limiting embodiment, the polishing layer can includepores such that polishing fluid can be at least partially absorbed bythe polishing layer. The number of pores can vary widely. In a furthernon-limiting embodiment, the number of pores can be such that thepolishing layer can be substantially non-porous and substantiallyimpermeable to polishing fluid. In alternate non-limiting embodiments,the polishing layer can have a porosity, expressed as percent porevolume, of at least two (2) percent by volume based on the total volumeof the polishing layer, or 50 percent or less by volume based on thetotal volume of the polishing layer. The percent pore volume of thepolishing pad can be determined using a variety of techniques known inthe art. In a non-limiting embodiment, the following expression can beused to calculate percent pore volume:100×(density of the pad)×(pore volume of the pad).

The density can be expressed in units of grams per cubic centimeter, andcan be determined by a variety of conventional methods known in the art.In a non-limiting embodiment, the density can be determined inaccordance with ASTM D 1622-88. The pore volume can be expressed inunits of cubic centimeters per gram, and can be determined usingconventional methods and equipment known in the art. In a non-limitingembodiment, pore volume can be measured in accordance with the mercuryporosimetry method in ASTM D 4284-88, using an Autopore III mercuryporosimeter from Micromeritics. In a further non-limiting embodiment,the pore volume measurements can be made under the following conditions:a contact angle of 140°; a mercury surface tension of 480 dynes/cm; anddegassing of the polishing pad sample under a vacuum of 50 micrometersof mercury.

In a non-limiting embodiment, the polishing layer can have at least apartially open cell structure such that it can absorb slurry. In afurther non-limiting embodiment, the cell structure can be such that thepolishing layer can be substantially non-absorbent. In alternatenon-limiting embodiments, the polishing layer can absorb at least 2percent by weight of polishing fluid based on the total weight of thepolishing layer, or not more than 50 percent by weight, or from 2percent by weight to 50 percent by weight.

The sublayer to which the polishing layer can be at least partiallyconnected, can increase the uniformity of contact between the polishingpad and the surface of the substrate being polishing. A consideration inselecting the material for the sublayer can be the ability of a materialto provide compliant support to the work surface of the polishing padsuch that the polishing layer can substantially conform to themacroscopic contour or long-term surface of the device being polished.Such material can be desirable for use as the sublayer in the polishingpad of the present invention.

The surface of a microelectronic substrate, such as a semiconductorwafer, can have a “wave” contour as a result of the manufacturingprocess. It is contemplated that if the polishing pad cannot adequatelyconform to the “wave” contour of the substrate surface, the uniformityof the polishing performance can be degraded. For example, if the padcan substantially conform to the ends of the “wave”, but cannotsubstantially conform to and contact the middle portion of the “wave”,only the ends of the “wave” can be substantially polished or planarizedand the middle portion can remain substantially unpolished orunplanarized.

In a non-limiting embodiment, the flexibility of the sublayer can besuch that the polishing layer can conform to the macroscopic orlong-term surface of the substrate being polished. The flexibility ofthe sublayer can vary widely. In a further non-limiting embodiment, thesublayer can be more flexible than the polishing layer. The flexibilityof the sublayer can be determined using various methods known to theskilled artisan. In a non-limiting embodiment, “flexibility” (F) can bedetermined by the inverse relationship of sublayer thickness cubed (t³)and the flexural modulus of the sublayer material (E), i.e. F=1/t³E. Inalternate non-limiting embodiments, the flexibility of the sublayer canbe greater than 1.0×10⁻⁸ in⁻¹lb⁻¹, or greater than 1.0×10⁻⁴ in ⁻¹lb⁻¹.

In a non-limiting embodiment, the sublayer can be softer than thepolishing layer. As used herein, “softness” refers to the Shore AHardness of the material. In general, the softer the material, the lowerthe Shore A Hardness value. Thus, in the present invention the Shore AHardness value of the sublayer can be lower than the Shore A Hardnessvalue of the polishing layer. In alternate non-limiting embodiments, thesublayer can have a Shore A Hardness of at least 15, or at least 45, or75 or less, or from 45 to 75. In further alternate non-limitingembodiments, the Shore A Hardness of the polishing layer can be at least85, or 99 or less, or from 85 to 99. The Shore A Hardness value can bedetermined using various methods and equipment known in the art. In anon-limiting embodiment, Shore A Hardness can be determined inaccordance with the procedure recited in ASTM D 2240, using a Shore“Type A” Durometer having a maximum indicator (available from PCTInstruments, Los Angeles, Calif.). In a non-limiting embodiment, thetest method for Shore A Hardness can include the penetration of aspecific type of indentor being forced into the test material underspecified conditions. In this embodiment, the Hardness can be inverselyrelated to the penetration depth and can be dependent on the elasticmodulus and viscoelastic behavior of the test material.

In another non-limiting embodiment of the present invention, thesublayer of the polishing pad can be more compressible than thepolishing layer. As used herein, “compressibility” refers to the percentvolume compressibility measurement. In a non-limiting embodiment, thepercent volume compressibility of the sublayer can be greater than thepercent volume compressibility of the polishing layer. In alternatenon-limiting embodiments, the percent volume compressibility of thesublayer can be less than 20 percent when a load of 20 psi is applied,or less than 10 percent when a load of 20 psi is applied, or less than 5percent when a load of 20 psi is applied. In another non-limitingembodiment, the percent volume compressibility of the polishing layercan be less than the percent volume compressibility of the sublayer. Ina further non-limiting embodiment, the percent volume compressibility ofthe polishing layer can be from 0.3 to 3 percent when a load of 20 psiis applied.

The percent volume compressibility of the sublayer can be determinedusing various methods known in the art. In a non-limiting embodiment,the percent volume compressibility of the sublayer can be determinedusing the following expression.$100 \times \frac{\left( {{{pad}\quad{volume}\quad{without}\quad{load}} - {{pad}\quad{volume}\quad{under}\quad{load}}} \right)}{\left( {{pad}\quad{volume}\quad{without}\quad{load}} \right)}$

In a non-limiting embodiment, if the area of the pad does not changewhen the load is placed on it, then the preceding equation for volumecompressibility can be expressed in terms of pad thickness by thefollowing expression.$100 \times \frac{\left( {{{pad}\quad{thickness}\quad{without}\quad{load}} - {{pad}\quad{thickness}\quad{under}\quad{load}}} \right)}{\left( {{pad}\quad{thickness}\quad{without}\quad{load}} \right)}$

The pad thickness can be determined using a variety of known methods. Ina non-limiting embodiment, the pad thickness can be determined byplacing a load (such as, but not limited to, calibrated weights) on thepad sample and measuring the change in thickness of the pad as a resultof the load. In a further non-limiting embodiment, a Mitutoyo ElectronicIndicator, Model ID-C112EB can be used. The indicator has a spindle orthreaded rod which can be fitted at one end with a flat contact underwhich the pad is placed. The spindle can be fitted at the other end witha device for applying specified loads to the contact area, such as butnot limited to a balance pan which accepts calibrated weights. TheIndicator displays the displacement of the pad resulting from applyingthe load. The Indicater display is typically representative of inches ormillimeters. The Electronic Indicator can be mounted on a MitutoyoPrecision Granite Stand to provide stability while taking themeasurements. The lateral dimensions of the pad can be sufficient topermit measurements at least 0.5″ from any edge. The surface of the padcan be flat and parallel over a sufficient area to permit uniformcontact between the test pad and the flat contact. The pad to be testedcan be placed under the flat contact. The thickness of the pad can bemeasured prior to applying the load. Calibrated balance weights can beadded to the balance pan for a specific resultant load. The pad then canbe compressed under the specified load. The Indicator can display thethickness/height of the pad under the specified load. The thickness ofthe pad prior to applying the load minus the thickness of the pad underthe specified load can be used to determine the displacement of the pad.In a non-limiting embodiment, a load of 20 psi can be applied to thepad. Measurements can be made at a standardized temperature such as roomtemperature. In a non-limiting embodiment, measurements can be taken ata temperature of 22° C. +/−2° C. This method of measuring thickness canbe applicable to a stacked pad construction or layer(s) comprising thestacked pad construction.

The sublayer can comprise a wide variety of materials known in the art.Suitable materials can include natural rubber, synthetic rubbers,thermoplastic elastomer, foam sheet and combinations thereof. Thematerial of the sublayer can be foamed or blown to produce a porousstructure. The porous structure can be open cell, closed cell, orcombinations thereof. Non-limiting examples of synthetic rubbers caninclude neoprene rubber, silicone rubber, chloroprene rubber,ethylene-propylene rubber, butyl rubber, polybutadiene rubber,polyisoprene rubber, EPDM polymers, styrene-butadiene copolymers,copolymers of ethylene and ethyl vinyl acetate, neoprene/vinyl nitrilerubber, neoprene/EPDM/SBR rubber, and combinations thereof. Non-limitingexamples of thermoplastic elastomers can include polyolefins,polyesters, polyamides, polyurethanes such as those based on polyethersand polyesters, and copolymers thereof. Non-limiting examples of foamsheet can include ethylene vinyl acetate sheets and polyethylene foamsheets; polyurethane foam sheets and polyolefin foam sheets, such as butnot limited to those which are available from Rogers Corporation,Woodstock, Conn.

In a further non-limiting embodiment, the sublayer can include non-wovenor woven fiber mat, and combinations thereof; such as but not limited topolyolefin, polyester, polyamide, or acrylic fibers, which have beenimpregnated with a resin. The fibers can be staple or substantiallycontinuous in the fiber mat. Non-limiting examples can include but arenot limited to non-woven fabric impregnated with polyurethane asdescribe in U.S. Pat. No. 4,728,552, such as polyurethane impregnatedfelt, which relevant portions of this Patent are incorporated herein byreference. A non-limiting example of a commercially available non-wovensubpad can be Suba™ IV, from Rodel, Inc. Newark Del.

The thickness of the sublayer can vary widely. In general, the padthickness can be such that the pad can be placed on and taken off of theplanarizing equipment with ease. If the pad is too thick, it can bedifficult to place on and take off of the planarizing equipment. Inalternate non-limiting embodiments, the sublayer can be at least 0.020inches thick, or at least 0.040 inches thick, or at least 0.045 inchesthick; or 0.100 or less inches thick, or 0.080 inches thick, or 0.065inches thick. In alternate non-limiting embodiments, the thickness ofthe polishing layer can be at least 0.040 inches, or at least 0.045inches, or 0.100 inches or less, or 0.080 inches or less, or 0.065inches or less.

In a non-limiting embodiment, the polishing pad construction can includea middle layer. In another non-limiting embodiment, the middle layer canfunction as a barrier to fluid transport between the polishing layer andthe sublayer. In a further non-limiting embodiment, the middle layer canbe essentially impermeable to the polishing fluid such that the sublayercannot become substantially saturated with polishing fluid.

In another non-limiting embodiment, the middle layer can function todistribute the compressive forces experienced by the polishing layerover a larger area of the sublayer. In a further non-limitingembodiment, the middle layer can be substantially non-volumecompressible.

In a non-limiting embodiment, the material for the middle layer can beselected such that the middle layer has the ability to substantiallyreduce or essentially prevent the transport of polishing fluid from thepolishing layer to the sublayer.

The middle layer can include a wide variety of materials known in theart. Suitable materials for the middle layer can include a wide varietyof substantially non-compressible polymers, and metallic films andfoils. Non-limiting examples of such polymers can include polyolefins,such as but not limited to low density polyethylene, high densitypolyethylene, ultra-high molecular weight polyethylene andpolypropylene; polyvinylchloride; cellulose-based polymers, such as butnot limited to cellulose acetate and cellulose butyrate; acrylic;polyesters and co-polyesters, such as but not limited to PET and PETG;polycarbonate; polyamide, such as nylon 6/6 and nylon 6/12; and highperformance plastics, such as polyetheretherketone, polyphenylene oxide,polysulfone, polyimide, and polyetherimide. Non-limiting examples ofmetallic films can include aluminum, copper, brass, nickel and stainlesssteel.

The thickness of the middle layer can vary widely. In alternatenon-limiting embodiments, the middle layer can have a thickness of atleast 0.0005 inches, or 0.0030 inches or less; or from 0.0010 to 0.0020inches.

In a non-limiting embodiment, the polishing layer and the sublayer ofthe present invention can be at least partially connected. In anotherembodiment, the polishing layer of the polishing pad can be at leastpartially connected to at least a portion of a middle layer and themiddle layer can be at least partially connected to at least a portionof the sublayer. The layers can be at least partially connected usingvarious means known in the art. In a further non-limiting embodiment,the connecting means can include an adhesive material.

Suitable adhesives for use in the present invention can be selected froma wide variety known in the art. In general, the adhesive should providesufficient peel resistance such that the pad layers essentially remainin place during use. Further, the adhesive should generally be able towithstand shear stresses which are present during the polishing orplanarization process and moreover, the adhesive should be able toresist chemical and moisture degradation during use. Non-limitingexamples of suitable adhesives can include contact adhesives, pressuresensitive adhesives, structural adhesives, hot melt adhesives,thermoplastic adhesives, curable adhesives such as but not limited tothermosetting adhesives, and combinations thereof. Non-limiting examplesof structural adhesives can include polyurethane adhesives and epoxyresin adhesives such as but not limited to those based on the diglycidylether of bisphenol A. Non-limiting examples of pressure sensitiveadhesives can include an elastomeric polymer and a tackifying resin.Non-limiting examples of elastomeric polymers can include naturalrubber, butyl rubber, chlorinated rubber, polyisobutylene, poly(vinylalkyl ethers), alkyd adhesives, acrylics such as but not limited tothose based on copolymers of 2-ethylhexyl acrylate and acrylic acid,block copolymers such as but not limited to styrene-butadiene-styrene,and mixtures thereof. In alternate non-limiting embodiments, a pressuresensitive adhesive can be applied to a substrate using an organicsolvent such as toluene or hexane, or from a water-based emulsion orfrom a melt. As used herein, the term “hot melt adhesive” refers to anadhesive comprised of a nonvolatile thermoplastic material that can beheated to a melt, then applied to a substrate as a liquid. Non-limitingexamples of hot melt adhesives can include ethylene-vinyl acetatecopolymers, styrene-butadiene copolymers, ethylene-ethyl acrylatecopolymers, polyesters, polyamides such as but not limited to thoseformed from the reaction of diamine and dimer acid, and polyurethanes.

In a non-limiting embodiment, the middle layer can include an adhesiveassembly. The adhesive assembly can include a middle layer interposedbetween an upper adhesive layer and a lower adhesive layer. In anon-limiting embodiment, the upper adhesive layer can be at leastpartially connected to the lower surface of the polishing layer, and thelower adhesive layer can be at least partially connected to the uppersurface of the sublayer. The upper, middle, and lower layers of theadhesive assembly can be selected from the aforementioned suitablematerials for the middle layer of the polishing pad. In a non-limitingembodiment, the upper and lower adhesive layers each can be contactadhesives. The adhesive assembly can be referred to in the art astwo-sided or double-coated tape. Non-limiting examples of commerciallyavailable adhesive assemblies include those from 3M, Industrial Tape andSpecialties Division.

In a non-limiting embodiment, the polishing pad of the present inventioncan include a polishing layer, a middle layer, and a sublayer wherein aportion of the polishing layer and sublayer includes an opening, and atleast a portion of the middle layer contains a window which can be atleast partially transparent to wavelengths used by the metrologyinstrumentation of polishing equipment. The polishing layer and sublayercan comprise an opening of suitable size, shape, and positioning suchthat it can be substantially aligned with the at least partiallytransparent window in the middle layer. The window of the middle layercan be recessed below the polishing surface by a distance substantiallyequal to the thickness of the polishing layer. The middle layercontaining the window can be at least partially coated on at least one,or two, of its surfaces with contact adhesive. The coating can provideany one of the following properties, for example: improved transparency,improved abrasion resistance, improved puncture resistance. In a furthernon-limiting embodiment, the openings of the polishing layer andsublayer can be at least partially aligned with the window; the lowersurface of the polishing layer can be pressed against one adhesivesurface, and the upper surface of the sublayer can be pressed againstthe other adhesive surface to form a pad construction. Any adhesiveadhering to the window surfaces can be at least partially removed withthe use of a solvent.

In alternate non-limiting embodiments, the opening can be produced byany suitable means known in the art, such as punching, die cutting,laser cutting or water jet cutting. In a further non-limitingembodiment, the opening can be formed by molding the polishing layerand/or sublayer such that an opening can be formed. In alternatenon-limiting embodiments, the opening in the polishing layer andsublayer can be produced prior to stacking the layers, or followingstacking of the layers. In a further non-limiting embodiment, theopening can be die cut into the polishing layer and/or sublayer, usingan NAEF Model B die press fitted with dies of suitable size and shape,which is commercially available from MS Instruments Company, StonyBrook, N.Y.

The size, shape, and location of the opening in the polishing layer andsublayer can vary widely and can depend upon the equipment being usedfor polishing. In a non-limiting embodiment, a Mirra polisher producedby Applied Materials Inc, Santa Clara Calif., can be used wherein theshape of the opening is a rectangle, having a size 0.5″×2″, beingpositioned with the long axis radially oriented and centered 4″ from thecenter of the pad. The platen for the Mirra polisher is 20″ in diameter.A pad for use with this polisher can comprise a circle of a 20-inchdiameter having a window area located in the area as described.

In another non-limiting embodiment, a Teres polisher commerciallyavailable from Lam Research Corporation, Fremont, Calif., can beemployed. This polisher uses a continuous belt instead of a circularplaten. The pad for this polisher can be a continuous belt of 12″ widthand 93.25″ circumference, which has a window suitably sized andpositioned to align with the metrology window of the Teres polisher.

In the present invention, the sublayer of the polishing pad can besubstantially permeable and/or porous such that it can absorb polishingfluid used during the polishing process. The sublayer can have an outerperipheral edge that is at least partially surface treated to reduceabsorption of polishing fluid through the outer peripheral edge. In anon-limiting embodiment, the surface treatment can minimize oressentially prevent absorption or permeation of polishing fluid into thesublayer through the outer peripheral edge. In a further non-limitingembodiment, the surface treatment can make at least a portion of thesurface of the outer peripheral edge of the sublayer substantiallyhydrophobic. In another non-limiting embodiment, the wettability of theouter peripheral edge of the sublayer can be reduced as a result of thesurface treatment.

In a non-limiting embodiment, the outer peripheral edge of the sublayerhaving surface treatment can at least partially absorb liquids otherthan polishing fluid such as but not limited to organic liquids. It isbelieved that such liquids can be absorbed because they generally havelower surface tension than polishing fluid. It is contemplated that thesurface-treated outer peripheral edge of the sublayer can absorb certainliquids because the pores in the sublayer are not substantially closedas a result of applying the surface treatment. Thus, it is furthercontemplated that if the pad were immersed in water, compressed and thenreleased, the pad could absorb water in a manner similar to a sponge.Thus, in a non-limiting embodiment, the physical properties of thesublayer such as but not limited to porosity, permeability, andcompressibility can be retained following surface treatment.

In a non-limiting embodiment, the surface treatment of the presentinvention can include applying to at least a portion of the surface ofthe outer peripheral edge of the sublayer, a material having the abilityto reduce the absorption or permeation of the polishing fluid by thesublayer through the outer peripheral edge. In a non-limitingembodiment, the surface treatment can render at least a portion of theouter peripheral edge of the sublayer hydrophobic. In anothernon-limiting embodiment, the surface treatment can reduce thewettability of the outer peripheral edge of the sublayer. It can beunderstood that in applying the material to at least a portion of thesurface of the outer peripheral edge of the sublayer, the material canextend onto at least a portion of a polishing layer or a middle layer ofthe polishing pad. Thus, in alternate non-limiting embodiments, thesurface of the peripheral edge of the polishing layer and/or middlelayer of the polishing pad can be at least partially coated with thematerial used in the surface treatment.

The material for use in the present invention can include a wide varietyof compounds known in the art. In a non-limiting embodiment, thematerial can include those compounds known in the art to render asubstrate substantially hydrophobic upon application of the material toat least a portion of the surface of the substrate. Suitable materialscan include silanes, organic polymers, silane-treated silicas, andmixtures thereof. Non-limiting examples of suitable silanes can includeorgano silanes such as but not limited to alkyl silanes, such as but notlimited to perflouro silanes, octyl silanes, chloro alkyl silanes, andmixtures thereof. Non-limiting examples of perfluoro silanes can includebut are not limited to(tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane;trichloro(1H,1H,2H,2H-perfluorooctyl)silane;(tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane;(3,3,3-trifluoropropyl)trichlorosilane;(3,3,3-trifluoropropyl)trimethoxysilane;(heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane;(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane;(3-heptafluoroisopropoxy) propyltrichlorosilane; and mixtures thereof.Non-limiting examples of suitable organic polymers can include but arenot limited to polyolefins such as but not limited to polyethylene andpolypropylene; fluoropolymers; and mixtures thereof. Non-limitingexamples of suitable silane-treated silica can include thosecommercially available under the trade name Aerosil R202 and AerosilR805.

In a non-limiting embodiment, the material used in surface treating thesublayer can include at least one perfluoroalkylalkyl silane asdisclosed in U.S. Pat. Nos. 4,997,684; 5,328,768 and 5,523,162; therelevant portions which are incorporated herein by reference. In afurther non-limiting embodiment, the material can include at least oneperfluoroalkylalkyl silane represented by the following formula R_(m)R′_(n) Si X_(4-m-n), wherein R can be a perfluoroalkylalkyl radical; mcan be 1, 2 or 3; n can be 0, 1, or 2; and m+n can be less than 4; R′can be a vinyl or an alkyl radical, such as but not limited to methyl,ethyl, vinyl or propyl; and X can be a radical such as but not limitedto halogen, acyloxy, or alkoxy. In alternate non-limiting embodiments,perfluoroalkyl moieties in the perfluoroalkylalkyl radicals can rangefrom CF₃ to C₃₀F₆₁, or C₆F₁₃ to C₁₈F₃₇, or C₈F₁₇ to C₁₂F₂₅. In furtheralternate non-limiting embodiments, the second alkyl moiety of theperfluoroalkylalkyl can be a substituted ethyl; R′ can be methyl orethyl; X can include hydrolyzable chloro, bromo, iodo, methoxy, ethoxyand acetoxy radicals. In another non-limiting embodiment,perfluoroalkylalkyl silanes can includeperfluoroalkylethyltrichlorosilane, perfluoroalkylethyltrimethoxysilane,perfluoroalkylethyltriacetoxysilane,perfluoroallkylethyidichloro(methyl)silane andperfluoroalkylethyldiethoxy(methyl)silane.

The material for use in surface treating the sublayer of the polishingpad of the present invention can include an integral primer which can beselected from a wide variety known in the art. In a non-limitingembodiment, the integral primer can be selected from the integralprimers disclosed in U.S. Pat. No. 5,523,161; and which relevantportions are incorporated herein by reference. In alternate non-limitingembodiments, the integral primer can be a hydrolyzable silane orsiloxane capable of hydrolytic condensation to form silica gel which canfunction as the integral primer.

Non-limiting examples of suitable silanes capable of hydrolysis tosilica gel can have the general formula SiX₄ wherein X can be ahydrolysable radical selected from halogens, alkoxy or acyloxy radicals.In alternate non-limiting embodiments, X can be chloro, bromo, iodo,methoxy, ethoxy and acetoxy. In another non-limiting embodiment,hydrolyzable silanes can include tetrachlorosilane, tetramethoxysilane,tetraacetoxysilane, and mixtures thereof.

Non-limiting examples of suitable siloxanes can include thoserepresented by the general formula Si_(y)O_(z)X_(4y-2z), wherein X canbe selected from halogen, alkoxy and acyloxy radicals, y can be two ormore, z can be one or more, and 4y-2z can be greater than zero. Inalternate non-limiting embodiments, hydrolysable siloxanes can includehexachlorodisiloxane, octachlorotrisiloxane, higher oligomerchlorosiloxanes, and mixtures thereof.

The surface treating material of the present invention can be at leastpartially applied to at least a portion of the surface of the outerperipheral edge of the sublayer using a variety of conventionaltechniques known to the skilled artisan. In alternate non-limitingembodiments, the material can be applied as a solution in solvent, orthe composition can be applied solvent-free. In alternate non-limitingembodiments, solvent can be present with the material in a surfacetreating composition in an amount of from 0 to 75 percent by weight ofthe composition, or from 0 to 50 percent by weight of the composition.Suitable solvents can include a wide variety known to the skilledartisan. In general, the solvent can be selected such that it iscompatible with the surface treating material being used. In anon-limiting embodiment, the solvent is an aprotic solvent such as butnot limited to an alkane or mixture of alkanes, or a fluorinatedsolvent. Further non-limiting examples of suitable solvents can includebut are not limited to isopropanol, ethanol, hexane, heptane, methylenechloride, acetone, toluene, naphtha, and mixtures thereof. In alternatenon-limiting embodiments, the solvent can include fluorinatedhydrocarbon solvents such as trichlorotrifluoroethane, perfluorinatedorganic compounds such as perfluorocarbons, and mixtures thereof. Inanother non-limiting embodiment, the solvent can be evaporated by dryingin air at ambient temperature. In a further non-limiting embodiment, thecomposition then can be cured by heating the treated surface.

In further alternate non-limiting embodiments, the surface treatmentmaterial can be applied by dipping, flowing or wiping. Following theapplication of the surface treatment, the pad can be protected againstphysical contact or abrading forces that could degrade the treatment fora period of time that can be referred to as a holding period. Theholding period can vary widely depending on the reactivity of thepolishing pad layers and the material used for the surface treatment. Ina non-limiting embodiment, the holding period can be at least 24 hoursor up to 96 hours. In a further non-limiting embodiment, the surfacetreatment can be applied under controlled relative humidity andtemperature conditions. These conditions can vary widely depending uponthe particular materials employed in the pad and the surface treatment.In alternate non-limiting embodiments, the relative humidity can be from30 to 80%, or from 35 to 55%. In other alternate non-limitingembodiments, the temperature can be from 50° F. to 85° F., or from 60°F. to 80° F.

The amount of surface treatment material applied to the surface of theouter peripheral edge of the sublayer can vary widely. In general, theamount of the material can be such that the absorption of polishingfluid through the outer peripheral edge of the sublayer can be reducedsuch that permeation of polishing fluid into the sublayer of the pad isreduced. In a non-limiting embodiment, the amount can be such that theouter peripheral edge of the sublayer is made substantially hydrophobic.Further, in another non-limiting embodiment, the amount can be such thatthe pores of the sublayer are not substantially closed.

The polishing pads of the present invention can be used in combinationwith a variety of polishing fluids, such as polishing slurries, whichare known in the art. Non-limiting examples of suitable slurries for usewith the pad of the present invention, include but are not limited tothe slurries disclosed in U.S. Pat. No. 6,656,241B1 issued Dec. 2, 2003,and U.S. patent applications having Ser. Nos. 09/882,549 and 10/627,776,filed on Jun. 14, 2001 and Jul. 28, 2003, respectively, and are pending.The relevant portions of this patent and these applications are hereinincorporated by reference. In a non-limiting embodiment, the polishingfluid can be interposed between the polishing layer of the pad and thesubstrate to be polished. The polishing or planarizing process caninclude moving the polishing pad relative to the substrate beingpolished. A variety of polishing fluids or slurries are known in theart. Non-limiting examples of suitable slurries for use in the presentinvention include slurries comprising abrasive particles. Abrasives thatcan be used in the slurries include particulate cerium oxide,particulate alumina, particulate silica and the like. Examples ofcommercial slurries for use in the polishing of semiconductor substratesinclude but are not limited to ILD1200 and ILD1300 available from Rodel,Inc. Newark Del. and Semi-Sperse AM100 and Semi-Sperse 12 available fromCabot Microelectronics Materials Division, Aurora, Ill.

In a non-limiting embodiment, the polishing pad of the present inventioncan be utilized with an apparatus for planarizing an article having anon-planar surface. The planarizing apparatus can include a retainingmeans for holding the article; and a motive power means for moving thepad and the retaining means with respect to the other such that movementof the pad and the retaining means causes the slurry and the planarizingsurface of the pad to contact and planarize the non-planar surface ofthe article. In a further non-limiting embodiment, the planarizingapparatus can include a means of renewing the polishing or planarizingsurface of the pad, such as but not limited to a mechanical arm equippedwith an abrasive disk which abrades the work surface of the pad.

In a non-limiting embodiment, the planarizing apparatus can include anapparatus for conducting in-situ metrology of the article being polishedor planarized. In general, in-situ metrology can include directing abeam of light through an at least partially transparent window locatedin the platen of the tool; the beam of light can be reflected off thesurface of the wafer, back trough the platen window, and into adetector. The polishing pad used with such apparatus can include awindow that is at least partially transparent to the wavelengths used inthe metrology system, and substantially aligned with the platen window.Commercial polishing or planarizing apparatuses are available fromequipment manufacturers such as Applied Materials, LAM Research,SpeedFam-IPEC, and Ebara Corp.

In a non-limiting embodiment, the pad of the present invention can beplaced on a cylindrical metal base; and can be connected to at least aportion of the base with a layer of adhesive. Suitable adhesives caninclude a wide variety of known adhesives. In a further non-limitingexample, the pad can be placed on the cylindrical metal base or platenof a polishing or planarizing apparatus that includes a means ofconducting in-situ metrology of the article being polished. The pad canbe placed such that its window area can be aligned with the metrologywindow of the platen.

EXAMPLES Example 1

Using a small sponge, micronized polypropylene in powder form was wipedonto the subpad outer peripheral edge of a stacked polishing padcommercially obtained from Rodel, Inc., Newark, Del., under the tradename IC1400. The micronized polypropylene was commercially obtained fromLubrizol Corporation, Wickliffe, Ohio under the trade name LancoPP1362D. Following application of the micronized polypropylene, thestacked pad was immersed in slurry for one hour. The slurry wascommercially obtained from Rodel, Inc., Newark, Del. under the tradename ILD 1300 Planarization Slurry. The pad was removed from the slurryand the outer peripheral edge was visually inspected. The outerperipheral edge of the subpad appeared dry.

Example 2

The process as described in Example 1 was carried out with the exceptionthat the micronized polypropylene was replaced with hydrophobic fumedsilica obtained from Degussa Corporation, Parsippany, N.J., under thetrade name Aerosil R805. The outer peripheral edge of the subpadappeared dry.

Example 3

Hydrophobic fumed silica commercially obtained from Degussa Corporation,Parsippany, N.J., under the trade name Aerosil R202, was dispersed inacetone at a concentration of one (1) weight percent. Using a Texwipeclean room swab, No. TX761, commercially obtained from FisherScientific, Pittsburgh, Pa., the solution was applied to the subpadouter peripheral edge of a 22.5-inch stacked polishing pad commerciallyobtained from Thomas West, Incorporated, under the trade name WESTPADS,Model No. STT 711-C561-22.5. The subpad edge was treated using 0.8 gramsof the 1% solution. Following application of treatment solution, the padstack was held at ambient conditions for 2 hours then immersed in ILD1300 slurry for one hour. The pad was then removed from the slurry andthe subpad outer peripheral edge was visually inspected. The outerperipheral edge of the subpad appeared dry.

Example 4

Using a small sponge, hydrophobic fumed silica commercially obtainedfrom Degussa Corporation, Parsippany, N.J., under the trade name AerosilR805, in powder form was wiped onto the surface of the outer peripheraledge of the subpad layer of a IC1000/SubaIV stacked polishing padcommercially obtained from Rodel, Inc., Newark, Del. The powder wasdeposited in the pores exposed at the surface and did not extent beyondthe surface of the outer peripheral edge. The stacked pad was thenimmersed in ILD 1300 slurry for one hour. The pad was removed from theslurry and the outer peripheral edge was visibly inspected. The outerperipheral edge of the subpad appeared dry.

Example 5

Using a Texwipe clean room swab, 0.3 grams oftrichloro(1H,1H,2H,2H-perfluorooctyl)silane in liquid form commerciallyobtained from Aldrich Chemical Company, Inc., Milwaukee, Wis. under thecatalog number 44,893-1, was wiped onto the subpad outer peripheral edgeof a 22.5-inch diameter IC1400 stacked polishing pad. Following theapplication, the pad stack was held at ambient conditions for two (2)hours then immersed in ILD 1300 slurry for one (1) hour. The pad wasremoved from the slurry and the outer peripheral edge was visuallyinspected. The outer peripheral edge of the subpad appeared dry.

Control 1 (untreated IC1400 subpad)

The process as described in Example 1 was carried out with the exceptionthat the micronized polypropylene was not applied.

The outer peripheral edge of the subpad appeared wet.

Control 2 (untreated WESTPADS subpad)

The process as described in Example 3 was carried out with the exceptionthat the hydrophobic fumed silica was not applied.

The outer peripheral edge of the subpad appeared wet.

Control 3 (untreated IC1000/SubaIV subpad)

The process as described in Example 4 was carried out with the exceptionthat the hydrophobic fumed silica was not applied.

The outer peripheral edge of the subpad appeared wet.

1. A polishing pad for use in polishing a microelectronic substratecomprising: a polishing layer adapted to polish said substrate; asublayer of substantially liquid permeable material, wherein saidpolishing layer and said sublayer are at least partially connected; andan outer peripheral edge of said sublayer wherein at least a portion ofsaid outer peripheral edge has a surface treatment, said surfacetreatment being effective to reduce absorption of polishing liquidthrough said outer peripheral edge.
 2. The polishing pad of claim 1wherein said polishing layer is substantially impermeable to polishingfluid.
 3. The polishing pad of claim 1 wherein said polishing layer issubstantially permeable to polishing fluid.
 4. The polishing pad ofclaim 1 wherein said sublayer is more compressible than said polishinglayer.
 5. The polishing pad of claim 1 wherein said sublayer comprisesmaterial chosen from natural rubber, synthetic rubbers, thermoplasticelastomer, foam sheet and combinations thereof.
 6. The polishing pad ofclaim 1 wherein said sublayer is connected to said polishing layer bymeans of a middle layer.
 7. The polishing pad of claim 6 wherein atleast a portion of said middle layer comprises a transparent material.8. The polishing pad of claim 7 wherein said sublayer and said polishinglayer contain an opening substantially aligned with said transparentportion of said middle layer.
 9. The polishing pad of claim 1 whereinsaid outer peripheral edge can absorb organic liquids.
 10. The polishingpad of claim 1 wherein said surface treatment comprises treatment ofsaid sublayer with at least one material chosen from silanes, organicpolymers, silane-treated silicas, and mixtures thereof.
 11. Thepolishing pad of claim 10 wherein said surface treatment comprisestreatment of said sublayer with at least one material chosen from alkylsilanes, polyolefins and mixtures thereof.
 12. A polishing pad for usein polishing a microelectronic substrate comprising: a polishing layeradapted to polish said substrate; a sublayer of substantially liquidpermeable material, wherein said polishing layer and said sublayer areat least partially connected; and an outer peripheral edge of saidsublayer wherein at least a portion of said outer peripheral edge has asurface treatment, said surface treatment being effective to render saidouter peripheral edge substantially hydrophobic.
 13. A polishing pad foruse in polishing a microelectronic substrate comprising: a polishinglayer adapted to polish said substrate; a sublayer of substantiallyliquid permeable material, wherein said polishing layer and saidsublayer are at least partially connected; and an outer peripheral edgeof said sublayer wherein at least a portion of said outer peripheraledge has a surface treatment, said surface treatment being effective toreduce the wettability of said outer peripheral edge.
 14. A method ofpolishing a microelectronic substrate comprising: surface treating anouter peripheral edge of a sublayer of a polishing pad, said pad beinguseful for polishing a microelectronic substrate and said sublayercomprising substantially liquid permeable material, wherein said surfacetreatment is effect to reduce the absorption of polishing fluid throughsaid outer peripheral edge.
 15. A method of polishing a microelectronicsubstrate comprising: at least partially applying to an outer peripheraledge of a sublayer of a polishing pad a surface treatment material, saidmaterial being effective to render said outer peripheral edgehydrophobic, said pad being useful for polishing a microelectronicsubstrate and said sublayer comprising substantially liquid permeablematerial.
 16. A method for reducing the absorption of polishing fluidthrough the outer peripheral edge of a sublayer of a polishing pad,comprising: surface treating at least a portion of said outer peripheraledge wherein said surface treating comprises applying to said outerperipheral edge of said sublayer at least one material chosen fromsilanes, organic polymers, silane-treated silicas, and mixtures thereof.